The instant invention pertains to methods and apparatus for moving pipe and more particularly to such a method and apparatus in which pipe or casing is moved from a horizontal position adjacent a well to a vertical position over the well bore.
In drilling an oil or gas well, drill pipe is typically stacked on racks in a horizontal position adjacent a drilling rig platform. One method for transferring pipe from the rack to the well platform comprises tying one end of a line on the rig around a selected pipe on the pipe rack. The pipe is thereafter lifted up onto the platform and the lower end thereof is placed into the mousehole. The mousehole is simply an upright, elongate cylindrical container adjacent the rotary table which supports the pipe temporarily. When it is necessary to add the pipe to the drill string, slips are secured about the drill string on the rotary table thereby supporting the same in the well bore. The pipe is disconnected from the traveling equipment and the elevators or the kelly are connected to the pipe in the mousehole. Next, the traveling block is raised thereby positioning the pipe over the drill string and tongs are used to secure the pipe to the upper end of the drill string. The drill pipe elevators suspend the drill pipe from a collar which is formed around one end of the pipe and do not clamp the pipe thereby permitting rotational pipe movement in order to threadably engage the same to the drill string.
There exist prior art apparatus for gripping a drill pipe on a pipe rack for moving the same into vertical alignment with a drill string suspended by slips from the rotary table. For example, U.S. Pat. No. 3,633,771 to Woolslayer et al. discloses an apparatus for moving drill pipe into and out of an oil well derrick. In Woolslayer, a stand of pipe is gripped by a strongback which is pivotally mounted to one end of a boom. The boom swings the strongback over the rotary table thereby vertically aligning the pipe stand with the drill string. When both adding pipe to and removing pipe from the drill string, all vertical movement of the pipe is accomplished by the elevators suspended from the traveling block.
A prior art technique for moving joints of casing from racks adjacent the drilling rig comprises tying a line from the rig onto one end of a selected casing joint on the rack. The line is raised thereby lifting the casing joint up a ramp leading to the rig platform. As the rope lifts the casing from the ramp, the lower end of the casing swings across the platform in a dangerous manner. The danger increases when a floating system is used in connection with offshore drilling. Since the rope is tied around the casing at one end thereof, the casing does not hang vertically but rather tilts somewhat. A man working on a platform elevated above the rig floor must hold the top of the casing and straighten it out while the casing is threaded onto the casing string which is suspended in the well bore by slips positioned on the rotary table.
It can be seen that it would be desirable to be able to grip casing or pipe positioned on a rack adjacent a drilling well, move the same into vertical orientation over the well bore and thereafter lower the same onto the string suspended in the well bore. It would also be desirable to utilize such a method and apparatus for transferring pipe from a rack adjacent the well to the mousehole on the rig platform during drilling. With respect to drill pipe, it would be desirable to have such a method and apparatus in which pipe could be transferred from the platform to the pipe rack.